The present invention relates generally to a sharpening apparatus for a dual-knife cutting mechanism of the type used to cut a continuously manufactured paper web and, more particularly, to a portable system for in-line sharpening the lower knife or cutter thereof.
As is well known in the art, paper is conventionally manufactured in a continuous web, several feet in width. The manufacturing equipment represents a huge capital investment, and the dynamics of the process are such that “downtime” is extremely costly.
As a part of this process, a dual-knife mechanism cuts the web longitudinally (i.e., in the direction of web travel) to provide rolls of the desired width or widths. For example, if 8½×11 inch paper is being made, the continuous web is cut into 8½ inch sections, individually rolled for further processing to the desired length of 11 inches.
Such dual-knife mechanisms are shown and described in U.S. Pat. Nos. 4,210,045; 4,274,319; and 4,658,685, and the teachings thereof are expressly incorporated herein by reference. An upper slitter unit, adjustably mounted on a substantially horizontal rail, includes a freely rotating blade, having a tapered peripheral edge. The lower slitter unit, secured to a motor-driven shaft, includes a collar having a tapered side edge. Engagement of blade and collar, or more particularly the blade and tapered side edge of the collar, cuts the paper web in a scissor-like action.
As the slitter units wear, the quality of the cut deteriorates, and maintenance is required. The upper slitter units are often removable from the rail, and sharpening is typically performed as normally scheduled maintenance, e.g., once a week. The associated downtime is usually measured in hours.
Maintenance of the lower slitter units represents a more difficult technical issue. To access the collars, the paper production system, in its entirety, must often be halted and the motor-driven shaft must be disengaged and pulled. Given the enormous weight of this shaft, an overhead crane is often required. The collars are then removed from the shaft and ground. Downtime for this operation can be several days.